But they haven't lasted that long; only the core structure remains. The majority of the pyramids has been stripped, gutted and vandalized. They're nothing like the original structures. And they're one of billions of man-made structures from the time that happen to still survive in a somehow recognizable form. If you're honest and calculate the actual half-life of human structures from that time period, you'll come to maybe a few decades at best.

This entire discussion feels a lot like the nuclear waste discussion how do you convey how bad we as a society are at conservation and planning ahead...